# File: number.py

class Number:
    def __init__(self, start):
        self.data = start
    def __sub__(self, other):
        return Number(self.data - other)
    def __getitem__(self, index):
        return index ** 2


class Indexer:
    data = [5, 6, 7, 8, 9]
    def __getitem__(self, index):
        print("getitem:", index)
        return self.data[index]


class IndexSetter:
    data = []
    def __getitem__(self, index):
        return self.data[index]
    def __setitem__(self, index, value):
        self.data[index] = value
